title: Copper Resistance in Pseudomonas syringae Strains Isolated from Mango Is Encoded Mainly by Plasmids.
abstract: ABSTRACT Bacterial apical necrosis of mango, elicited by Pseudomonas syringae pv. syringae, limits fruit production in southern Spain and Portugal. Examination of a collection of P. syringae pv. syringae isolates for copper resistance showed that 59% were resistant to cupric sulfate. The survey of a mango orchard revealed an increase in frequencies of copper-resistant bacteria after repeated treatments with Bordeaux mixture. These data suggest that selection of copper-resistant strains could be a major reason for control failures following management with copper bactericides. Most copper-resistant isolates harbored plasmids, although the majority of them contained a 62-kb plasmid that also was present in copper-sensitive strains. The 62-kb plasmids were differentiated by restriction enzyme analysis and hybridization to copABCD DNA. The most frequently found copper-resistant plasmid type (62.1) was transferable by conjugation. Southern blot hybridizations showed that genetic determinants partially homologous to copABCD were present in all the copper-resistant strains examined, and usually were associated with plasmids; these determinants were not detected in copper-sensitive strains. The selective pressure exerted by copper bactericide sprays on the diversity of copper resistance determinants in bacterial populations of mango is discussed.
authors.forename: Francisco M
authors.initials: FM
authors.lastname: Cazorla
authors.forename: Eva
authors.initials: E
authors.lastname: Arrebola
authors.forename: Ane
authors.initials: A
authors.lastname: Sesma
authors.forename: Alejandro
authors.initials: A
authors.lastname: Pérez-García
authors.forename: Juan C
authors.initials: JC
authors.lastname: Codina
authors.forename: Jesús
authors.initials: J
authors.lastname: Murillo
authors.forename: Antonio
authors.initials: A
authors.lastname: de Vicente